Rupert Neve Designs – Portico II Master Buss Processor – Some Thoughts

Fluid Mastering‘s Nick Watson talks about his initial impressions of this new addition to our main mastering studio.

Last Summer we tried out a couple of new bits of mastering kit; and we liked them both so much that we kept them.  In this post I’m going to tell you about the Portico II Master Buss Processor by Rupert Neve Designs, which is a bit of a mouthful, so let’s just call it the MBP.

Oh, and this isn’t a review, ‘coz I don’t know how to write those. I’m not going to try and provide an all-round assessment of the MBP in a range of applications, rather I’m just going to talk about what I like and don’t like about the MBP at this early stage in our relationship, and how I’m using it in the studio.

So, What Does It Do?

The MBP is a compressor with knobs on (ok, all compressors have knobs on, but you know what I mean). It’s a stereo processor intended for insertion into a master buss or for use in a mastering chain which provides compression, limiting, harmonic exciters and stereo width enhancement.

I’ll come clean right from the outset and tell you that we bought this fella because we love the compressor. You could strip the other stuff out of it and we’d still have wanted it for the compression alone, which is versatile, fun, funky and worlds apart from the Prism MLA-2 which is our other bit of go-to gear when it comes to handling dynamics in the analogue domain.

The Compressor

The MBP compressor is very effective in a range of applications and genres; for Rock, Pop & Dance it can have a way of hoisting up the beat and making it bold and upfront; especially handy if the drums were a bit limp or unstable sounding before, whilst for Classical and Jazz it can provide just the right amount of richness and control without sacrificing natural performance dynamics.

The compression section on the front panel offers the expected attack, release, ratio and threshold controls, but in addition to these there are two very useful features that I think every mastering compressor should have although many don’t: a high pass filter and a blend pot.

The high pass filter (which of course only affects the side-chain) is set at 250Hz, with what I presume is a fairly gentle slope. For me this is essential, especially as the norm these days is to have a fair amount of bass in a master. If you can’t filter this out of the side-chain, a compressor will tend to respond too much to the bass content; the potential consequences of which are unwanted pumping or flinching. With the HP filter engaged, the bass content in the side chain is reduced such that the amplitude and energy during bass peaks is more in line with how we perceive the sound, and the compression acts accordingly. The net effect of this is that those all-important downbeats come through clear and strong. For more flexible adjustments to the side-chain signal, the MBP also provides a switchable insert option, but for mastering I reckon the 250Hz filter does the job nicely.

The blend control mixes the unaffected signal with the compressed signal, providing a parallel compression mode. This could be achieved with external routing and summing, but having it on-board like this is a very clean and convenient solution. I’m a huge fan.

Tip: How I use parallel compression. Often I like to use compression to add richness and stability to a mix, but I don’t want the dynamic peaks in the performance to be attenuated. This is where parallel does the business. My approach to this is to start with straight compression (with the blend control at 100%), and set the parameters such that I’m getting a richness and punch that I like most of the time – with the quietest moments uncompressed, the loudest moments perhaps a little held-back, but everything in between sounding rich, punchy and controlled. Next, I set the make-up gain to a level where it is comparable to the dry signal. To be specific, I want the compressed signal to be louder than the dry signal when the music is quietest and the compressor is acting least, but at the loudest moments when the compressor is perhaps over-attenuating a little, I want the dry signal to be the louder of the two. Once I’ve found that sweet spot it’s usually a question of setting the blend control to around 50% to achieve the ideal balance between the compressed and uncompressed signals. With this approach, I find that (a) quieter or weaker moments are enhanced, as are transient peaks, whilst (b) louder moments like big vocal lines or instrumental swells are not compromised because the uncompressed signal takes precedence.

Two further controls act in the compressor section; firstly a Feed Back / Feed Forward selector toggles between a classic feed-back configuration (where the output of the VCA is used to control the gain changing element) and a more “modern” feed-forward configuration. Secondly, an RMS / Peak selector (as you might expect) toggles between gain reduction in response to the RMS level or peak amplitude. Personally, I’m finding the Feed-Back mode with RMS detection (which is the most traditional setup) to be most frequently applicable to mastering, although there have been exceptions.

Harmonics

If you’re familiar with other units in Rupert Neve Designs’ original Portico range, then you will have come across the “Silk” circuit which essentially acts as a harmonic exciter. The MBP takes the concept further, providing two “Silk” modes, each of which act upon the negative feedback on the output transformer in order to increase harmonic content. I like this feature, although this is also where my first criticism of the unit arises.

A single button toggles between three states: SILK (Blue), SILK+ (Red) and OUT, and a single pot labelled “Texture” controls the amount of the effect. Silk (Blue) focusses on mid and high frequency saturation, making the signal brighter in a broadly similar way to a traditional harmonic exciter. Silk+ (Red) acts more in the lower range of the spectrum, and is thus somewhat more subtle.

So far, I have found that the Red mode can add a sense of warmth and fullness when used with care although it can make things muddy if pushed too far. The Blue mode is more frequently useful and adds presence and zing, but when applied in excess can make things a bit gritty. My caveat is that “Silk” is quite difficult to set up for mastering for two reasons; one is that you can’t simply A/B between the affected and unaffected signal, because the push-button selector rotates between three states rather than allowing you a straight IN/BYPASS option. Also, even if you could A/B the effect, the affected signal is always louder, which makes it difficult to make an objective evaluation on the fly.

Personally, I find that if I want to achieve these kinds of effects, my chosen tool is usually the Culture Vulture (mastering PLUS) by Thermionic Culture (of which more in another post still to come) and so I’m not too bothered about the Silk feature on the MBP. I do use it sometimes however – if the Culture Vulture isn’t giving me what I want for whatever reason, a little Silk can be just the ticket.

The Limiter

In addition to the compressor, a second layer of dynamic control is available in the form of an “independent” limiter, which the manual describes as “extremely intelligent”. Scary.

What they’re getting at is that the limiter, like many others these days, is able to adapt to the incoming signal in order to provide optimised attack and release times from moment to moment.

Now, there’s no denying that this is a great limiter; possibly the best analogue limiter I’ve heard; but to be honest I haven’t found it to be particularly useful or it might be fairer to say that as yet I haven’t found a beneficial way of incorporating it into my work-flow. The issue I have with it is that it appears before the compressor’s blend control, so taking the unit as a whole, the MBP fails to act as a true limiter unless the blend is at 100% (which is rare, for me at least). Secondly, the gain reduction meters on the MBP are only capable of giving an indication of the total combined gain reduction provided by both compressor and limiter, which means that in terms of visual cues you have no idea which is doing what.

It seems to me, given that a Master Compressor is usually used in “link” mode providing equal amounts of gain reduction to both channels, that rather than having two meters (Left/Right) showing the same information as each other; a better idea would have been to have allocated one gain reduction meter to the compressor and the other meter to the limiter. Just sayin’…

Stereo Image

Finally we come to the MBP’s “Stereo Field Editor” section, which uses M-S techniques to affect the stereo image. As well as the more obvious width control provided by applying attenuation or gain to the Mid and Side signals, there is also an EQ element here which allows you to apply filters to the signal you’re adding or cutting. For me, the unit comes somewhat unstuck here for a number of reasons, although I’ve spoken to other Mastering Engineers who rather like it.

The EQ available is provided by way of a rotary control allowing you to select one of two shelving filters (high and low, at fixed frequencies) or two bandpass filters, which are labelled as HM and LM (high mid and low mid, also at fixed frequencies). The labelling is misleading however, as the “high mid” filter actually has a slightly lower centre frequency than the “low mid”, and vice versa. The main difference between them is not the centre frequency, but the bandwidth (one being somewhat wider than the other). Upon enquiring with the manufacturers as to why they used the terms HM and LM to differentiate the bands when the actual functionality is contrary to this, I was told that the terms HM and LM were considered less confusing because they were more familiar to users. Um…  okay…

In use, once I’d gotten past the fact that the EQ doesn’t necessarily do what the labelling led me to expect, the effect was ok, but just not very versatile. I tend to do my M-S work in the digital domain, applying EQ to the mid or side signals in a very targeted way using fully parametric EQ. To be limited to one of a choice of four fixed-frequency fixed-bandwidth filters just doesn’t give me the control I’m looking for, so I’ll be sticking with other techniques and tools that I know work for me.

A last word on the Stereo Field Editor; there is the option to switch the unit to “SFE to Comp” mode, which routes the mid-side signals through the compressor. However, in use I found that it doesn’t do so in the way you would expect, and in practise the width and depth controls act rather like a mix control when in this mode, blending the processed signal with a fixed-level dry signal (in anti-phase if you rotate anticlockwise). This produced some quite unpredictable results, and in practice I couldn’t achieve even subtle compression without adjusting the width or depth controls to the point where a significant gain change at the output made meaningful A/B comparisons nigh on impossible.  I do like my A/B comparisons, but then I’m a mastering engineer so I would.

To conclude…

I seriously love the MBP. I know I’ve said some rotten things about it, but I love it like a girlfriend with a wonky tooth or peculiar taste in shoes. I don’t care about the Stereo Field Editor, I don’t really need the Limiter, and I’m sufficiently familiar with the Silk function that I can live without convenient A/B ing. The point here is that this is a truly excellent compressor that does great things to music and I’d be heartbroken if I woke up one morning to find that we didn’t really have one.

Nick Watson.